A work machine such as an agricultural tractor may include an internal combustion (IC) engine which provides input power to a transmission, which in turn is coupled with and drives the rear axles through a rear end differential. The transmission, rear end differential and rear axles are sometimes referred to as the “rear end” of the work machine. The transmission typically is attached to the front of and provides input power to the rear end differential. The rear end differential provides ground power to the two rear axles, and also usually includes at least one power take-off (PTO) shaft extending rearwardly within the three point hitch arrangement at the rear of the tractor.
With a work machine as described above, it is common to provide a transmission with multiple shift ranges. Typically one shift lever is used to shift between multiple gear ranges (e.g., A, B, C and D gear ranges), and a second shift lever is used to shift between discrete gear pairs within each range (e.g., 1, 2, 3 or 4). The assignee of the present invention also markets a “PowerShift” series transmission in which at least one shift lever need not be foot clutched to shift “on-the-fly” during use. Variants of the PowerShift transmission go back to the 4020 series tractors manufactured in the 1960's.
Many transmissions used with work machines as described above include multiple shift elements (two or more gear pairs) which are shifted to place the transmission in a selected gear range and gear. Shifting multiple shift elements can be complex and difficult.
What is needed in the art is a transmission which is easier and simpler to shift during operation.